Energy balance and greenhouse gas emissions in an agroforestry system - a case study from Eastern Germany.

Following a cradle-to-farm-gate approach, we determined the input of fossil energy and greenhouse gas emissions (GGE) for conventional and agroforestry land use on a farm in a low profit region of Germany. On the basis of a calculation model with a recurring crop rotation of maize, rye, oat, and a catch crop mixture, it was found that a short rotation alley cropping system (SRACS) with a 10% (A10) and a 40% (A40) tree area for bioenergy production consumed 7% and 32% less fossil energy than the conventionally managed site (C). Simultaneously, the net energy gains and energy efficiency of the plant production process were increased by up to 8 and 53%, respectively. Likewise, the operational GGE accumulated to 3.1 Mg ha−1 yr−1 under C farming and could be reduced by 9% and 36% in A10 and A40, respectively. Overall, a multidimensional land use indicator comparison proved that under specific site conditions agroforestry land use can increase the energy output per unit of land area, while the energy input and GGE per metric ton of biomass yield were considerably lower than in C farming. Nominal range sensitivity analysis revealed that the energetic and ecological performance of the system was highly sensitive to the size and productivity of the tree area as well as to the use of fertilisers. Our findings suggest that SRACS may fundamentally improve the environmental and energetic performance of the cultivation process on marginal land, without leading to substantial losses in agricultural livestock production area. [ABSTRACT FROM AUTHOR]